1. Field of the Invention
The present invention relates to a position authentication system and electronic equipment using the same and particularly, to a position authentication system for authenticating latitude/longitude information of a positioning system using latitude/longitude information of GPS (Global Positioning System), and electronic equipment using the same.
2. Description of the Related Art
GPS (Global Positioning System) has been broadly known as one of methods for specifying the position of a mobile unit. In GPS, the position of a mobile unit on the plane can be specified by measuring the apparent distances from a mobile unit to each of three or more artificial satellites which transmit GPS signals (GPS satellites), and the position of the mobile unit in the height direction can be also specified by using four or more GPS satellites.
GPS is not only used for the position specification of mobile units such as a car, a ship, or an air plane, but also applied to various equipment. For example, Japanese Laid-open Patent Publication No. Hei-8-240852 discloses a camera in which position information and time information on a photographing position are obtained by using GPS and the information thus obtained is recorded along with an image on a film, and a filing device for filing photographic images taken by the camera. Further, Japanese Laid-open Patent Publication No. Hei-11-055741 discloses a method for obtaining position information by using GPS in a mobile computing terminal having a communication function, and registering the position information in a position information management center to unitarily manage the moving statuses of persons, vehicles, or the like every registration group.
However, the conventional equipment for specifying the position information and the time information by using GPS has no means for authenticating whether the position information and the time information are right or not.
Digital data (images) taken by a digital camera can be easily tampered by a computer, and thus reliability to the photographed digital images as evidence may be degraded (for example, accident records, construction records of construction works). In order to avoid this disadvantage, Japanese Laid-open Patent Publication No. Hei-10-164549 discloses an image authentication system of supplying authentication information on the identity of the photographed digital image data in such a style as to be integral with and inseparable from the digital image data.
According to the conventional image authentication system, an image is divided into two areas (first and second areas), and authentication information is generated from the image data in one (first) area (hereinafter referred to as “first-area image data”). The authentication information thus generated is hidden into the image data in the other (second) area (hereinafter referred to as “second-area image data”), the second-area image data containing the authentication information are combined with the first-area image data, and then the combined image data are recorded. When the identity is authenticated, first authentication information is generated from the first-area image data, the authentication information hidden in the second-area image data (second authentication information) is extracted from the second-area image data, and both the authentication information pieces are collated with each other. If both are coincident with each other, it is judged that the image is not tampered. Therefore, authentication means must be provided every terminal for judging the identity, and thus the cost of the terminal rises up. The above-described conventional image authentication system does not disclose the authentication of position information and time information obtained by using GPS.